• noun:   an agent that operates some apparatus or machine

  Example: "The operator of the switchboard"

• noun:   someone who owns or operates a business

  Example: "Who is the operator of this franchise?"

• noun:   a speculator who trades aggressively on stock or commodity markets
• noun:   (mathematics) a symbol that represents a function from functions to functions

  Example: "The integral operator"

• noun:   a shrewd or unscrupulous person who knows how to circumvent difficulties

Related words...